1. Field of the Invention
The field of art to which this invention pertains includes fluid pressure operated mechanisms and more specifically multiple disc wet brakes and clutches.
2. Description of the Prior Art
Multiple disc wet brakes and clutches utilize disc packs that include a plurality of axially movable first discs having projections extending radially outwardly into an engagement with a housing. A plurality of axially movable second discs, intermediate adjacent ones of the first discs, have projections extending radially inward into engagement with a rotatable hub portion. In some applications, the second discs are provided with friction material on their oppositely disposed annular surfaces. These mechanisms are generally hydraulically actuated via a piston that is hydraulically pressurized. The friction developed between the interfacing surfaces of the first and second pluralities of discs restrains the rotation of the rotatable hub in a manner well known in the art.
Wet disc brakes of this type are often used in heavy duty vehicles, especially in conjunction with planetary axle ends wherein the rotatable hub is generally drivingly connected or integral with a rotating wheel hub. When it becomes necessary to service wheel hub bearings or oil seals, the wheel hub and consequently the rotatable brake hub are removed from the axle housing. Removal of the brake hub causes the pluralities of second discs to loose their vertical location relative to the brake hub. This is especially true in designs where, in order to permit unimpeded coolant flow between the disc pack and its housing, there is a significant annular cooling fluid clearance between the outer peripheral surface of the disc pack and its housing. It is the utilization of this cooling fluid clearance that will cause a vertical downward displacement of these second brake discs until there is physical abutment between the outer annular surfaces of the discs with the inner peripheral surface of the housing at their lowest vertical point. This vertical displacement of the second discs, of course, represents problems upon the attempted reinsertion of the brake hub upon the reassembly of the axle end.
Prior art attempts to alleviate the previously mentioned problem include the use of a separate splined pilot stub shaft for lining up or positively locating the second brake discs. One of several methods for use of this stub shaft includes the pressurization of the brake (so as to immobilize the first and second brake discs); removing the wheel hub while the brake is still pressurized; inserting the stub shaft while the brake is still pressurized; depressurizing the brake so that the necessary maintenance procedures can be carried out; repressurizing the brake; removing the stub shaft while the brakes are still pressurized; and finally, reassembling the axle end and thereby reinsert the brake hub portion within the clutch pack and thereafter depressurizing the brake.